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CHAPTER
1
The Science of Macroeconomics
The whole of science is nothing more than the refinement of everyday thinking.
—Albert Einstein
W
hen Albert Einstein made the above observation about the nature
of science, he was probably referring to physics, chemistry, and
other natural sciences. But the statement is equally true when
applied to social sciences like economics. As a participant in the economy, and as
a citizen in a democracy, you cannot help but think about economic issues as you
go about your life or when you enter the voting booth. But if you are like most
people, your everyday thinking about economics has probably been casual rather
than rigorous (or at least it was before you took your first economics course).
The goal of studying economics is to refine that thinking.This book aims to help
you in that endeavor, focusing on the part of the field called macroeconomics,
which studies the forces that influence the economy as a whole.
1-1 What Macroeconomists Study
Why have some countries experienced rapid growth in incomes over the past
century while others have stayed mired in poverty? Why do some countries have
high rates of inflation while others maintain stable prices? Why do all countries
experience recessions and depressions—recurrent periods of falling incomes and
rising u
­ nemployment—and how can government policy reduce the frequency
and severity of these episodes? Macroeconomics attempts to answer these and
many related questions.
To appreciate the importance of macroeconomics, you need only head over to some
online news Web site. Every day you can see headlines such as INCOME GROWTH
REBOUNDS, FED MOVES TO COMBAT INFLATION, or STOCKS FALL
AMID RECESSION FEARS. These macroeconomic events may seem abstract,
but they touch all of our lives. Business executives forecasting the demand for their
products must guess how fast consumers’ incomes will grow. Senior citizens living on
fixed incomes wonder how fast prices will rise. Recent college graduates looking for
jobs hope that the economy will boom and that firms will be hiring.
1
2 | P A R T
I
Introduction
Because the state of the economy affects everyone, macroeconomic issues play
a central role in national political debates.Voters are aware of how the economy
is doing, and they know that government policy can affect the economy in
­powerful ways. As a result, the popularity of an incumbent president often rises
when the economy is doing well and falls when it is doing poorly.
Macroeconomic issues are also central to world politics, and the international
news is filled with macroeconomic questions. Was it a good move for much of
Europe to adopt a common currency? Should China maintain a fixed exchange
rate against the U.S. dollar? Why is the United States running large trade deficits?
How can poor nations raise their standards of living? When world leaders meet,
these topics are often high on their agenda.
Although the job of making economic policy belongs to world leaders, the
job of explaining the workings of the economy as a whole falls to macroeconomists. Toward this end, macroeconomists collect data on incomes, prices, unemployment, and many other variables from different time periods and ­different
countries. They then attempt to formulate general theories to explain these
data. Like astronomers studying the evolution of stars or biologists studying the
evolution of species, macroeconomists cannot conduct controlled experiments
in a laboratory. Instead, they must make use of the data that history gives them.
Macroeconomists observe that economies differ across countries and that they
change over time. These observations provide both the motivation for developing macroeconomic theories and the data for testing them.
To be sure, macroeconomics is an imperfect science. The macroeconomist’s
ability to predict the future course of economic events is no better than the
meteorologist’s ability to predict next month’s weather. But, as you will see, macroeconomists know quite a lot about how economies work. This knowledge is
useful both for explaining economic events and for formulating economic policy.
Every era has its own economic problems. In the 1970s, Presidents Richard
Nixon, Gerald Ford, and Jimmy Carter all wrestled in vain with a rising rate of
inflation. In the 1980s, inflation subsided, but Presidents Ronald Reagan and
George H. W. Bush presided over large federal budget deficits. In the 1990s, with
President Bill Clinton in the Oval Office, the economy and stock market enjoyed
a remarkable boom, and the federal budget turned from deficit to surplus. As
Clinton left office, however, the stock market was in retreat, and the economy was
heading into recession. In 2001 President George W. Bush reduced taxes to help
end the recession, but the tax cuts contributed to a reemergence of budget deficits.
President Barack Obama moved into the White House in 2009 during a period
of heightened economic turbulence. The economy was reeling from a financial
crisis, driven by a large drop in housing prices, a steep rise in mortgage defaults,
and the bankruptcy or near-bankruptcy of many financial institutions. As the
financial crisis spread, it raised the specter of the Great Depression of the 1930s,
when in its worst year one out of four Americans who wanted to work could not
find a job. In 2008 and 2009, officials in the Treasury, Federal Reserve, and other
parts of government acted vigorously to prevent a recurrence of that outcome.
And while they succeeded—the unemployment rate peaked at 10 percent—the
downturn was nonetheless severe, the subsequent recovery was painfully slow, and
the policies enacted left a legacy of greatly expanded government debt.
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The Science of Macroeconomics | 3
Macroeconomic history is not a simple story, but it provides a rich motivation
for macroeconomic theory.While the basic principles of macroeconomics do not
change from decade to decade, the macroeconomist must apply these principles
with flexibility and creativity to meet changing circumstances.
CASE STUDY
The Historical Performance of the U.S. Economy
Economists use many types of data to measure the performance of an economy.Three
macroeconomic variables are especially important: real gross domestic product (GDP),
the inflation rate, and the unemployment rate. Real GDP measures the total income
of everyone in the economy (adjusted for the level of prices). The inflation rate
measures how fast prices are rising. The unemployment rate measures the fraction
of the labor force that is out of work. Macroeconomists study how these variables are
determined, why they change over time, and how they interact with one another.
Figure 1-1 shows real GDP per person in the United States. Two aspects of
this figure are noteworthy. First, real GDP grows over time. Real GDP per person
FIGURE 1 -1
Real GDP per person
(2009 dollars)
50,000
World
War I
Great World Korean
Depression War II War
Vietnam
War
First oil-price shock
Second oil-price
shock
40,000
Financial
crisis
20,000
9/11
terrorist
attack
10,000
5,000
1900 1910
1920
1930
1940
1950
1960
1970
1980
1990
2000
2010
Year
Real GDP per Person in the U.S. Economy Real GDP measures
the total income of everyone in the economy, and real GDP per
person measures the income of the average person in the economy.
This figure shows that real GDP per person tends to grow over time
and that this normal growth is sometimes interrupted by periods of
declining income, called recessions or depressions.
Note: Real GDP is plotted here on a logarithmic scale. On such a scale, equal
distances on the vertical axis represent equal percentage changes. Thus, the
distance between $5,000 and $10,000 (a 100 percent change) is the same as the
distance between $10,000 and $20,000 (a 100 percent change).
Data from: U.S. Department of Commerce, Economic History Association.
4 | P A R T
I
Introduction
FIGURE 1-2
Percent
30
World
War I
25
Great
Depression
World Korean
War II War
Vietnam
War
First oil-price shock
Second oil-price shock
Financial
crisis
20
Inflation
15
9/11
terrorist
attack
10
5
0
–5
Deflation
–10
–15
–20
1900
1910
1920
1930
1940
1950
1960
1970
1980
1990
2000
2010
Year
The Inflation Rate in the U.S. Economy The inflation rate measures the percent-
age change in the average level of prices from the year before. When the inflation
rate is above zero, prices are rising. When it is below zero, prices are falling. If the
inflation rate declines but remains positive, prices are rising but at a slower rate.
Note: The inflation rate is measured here using the GDP deflator.
Data from: U.S. Department of Commerce, Economic History Association
today is about eight times higher than it was in 1900. This growth in average
income allows us to enjoy a much higher standard of living than our greatgrandparents did. Second, although real GDP rises in most years, this growth
is not steady. There are repeated periods during which real GDP falls, the most
dramatic instance being the early 1930s. Such periods are called recessions if
they are mild and depressions if they are more severe. Not surprisingly, periods
of declining income are associated with substantial economic hardship.
Figure 1-2 shows the U.S. inflation rate.You can see that inflation varies substantially over time. In the first half of the twentieth century, the inflation rate averaged
only slightly above zero. Periods of falling prices, called deflation, were almost as
common as periods of rising prices. By contrast, inflation has been the norm during the past half century. Inflation became most severe during the late 1970s, when
prices rose at a rate of almost 10 percent per year. In recent years, the inflation rate
has been about 2 percent per year, indicating that prices have been fairly stable.
Figure 1-3 shows the U.S. unemployment rate. Notice that there is always
some unemployment in the economy. In addition, although the unemployment
rate has no long-term trend, it varies substantially from year to year. Recessions
CHAP T E R
FIGURE 1
The Science of Macroeconomics | 5
1 -3
Percent unemployed
World
War I
Great
World Korean
Depression War II War
Vietnam
War
First oil-price shock
Second oil-price shock
25
Financial
crisis
20
9/11
terrorist
attack
15
10
5
0
1900 1910
1920
1930
1940
1950
1960
1970
1980
1990
2000
2010
Year
The Unemployment Rate in the U.S. Economy The unemployment rate ­measures
the percentage of people in the labor force who do not have jobs. This figure shows
that the economy always has some unemployment and that the amount fluctuates
from year to year.
Data from: U.S. Department of Labor, U.S. Census Bureau.
and depressions are associated with unusually high unemployment. The highest rates of unemployment were reached during the Great Depression of the
1930s. The worst economic downturn since the Great Depression occurred in
the aftermath of the financial crisis of 2008–2009, when unemployment rose
substantially. Even several years after the crisis, unemployment remained high.
These three figures offer a glimpse at the history of the U.S. economy. In the
chapters that follow, we first discuss how these variables are measured and then
develop theories to explain how they behave. n
1-2 How Economists Think
Economists often study politically charged issues, but they try to address these
issues with a scientist’s objectivity. Like any science, economics has its own set
of tools—terminology, data, and a way of thinking—that can seem foreign and
arcane to the layman. The best way to become familiar with these tools is to
practice using them, and this book affords you ample opportunity to do so. To
make these tools less forbidding, however, let’s discuss a few of them here.
6 | P A R T
I
Introduction
Theory as Model Building
Young children learn much about the world around them by playing with toy
versions of real objects. For instance, they often put together models of cars,
trains, or planes. These models are far from realistic, but the model-builder learns
a lot from them nonetheless.The model illustrates the essence of the real object it
is designed to resemble. (In addition, for many children, building models is fun.)
Economists also use models to understand the world, but an economist’s
model is more likely to be made of symbols and equations than plastic and glue.
Economists build their “toy economies” to help explain economic variables,
such as GDP, inflation, and unemployment. Economic models illustrate, often
in mathematical terms, the relationships among the variables. Models are useful
because they help us dispense with irrelevant details and focus on underlying
connections. (In addition, for many economists, building models is fun.)
Models have two kinds of variables: endogenous variables and exogenous variables. Endogenous variables are those variables that a model tries to explain.
Exogenous variables are those variables that a model takes as given. The purpose of a model is to show how the exogenous variables affect the endogenous
variables. In other words, as Figure 1-4 illustrates, exogenous variables come from
outside the model and serve as the model’s input, whereas endogenous variables
are determined within the model and are the model’s output.
To make these ideas more concrete, let’s review the most celebrated of all
economic models—the model of supply and demand. Imagine that an economist
wants to figure out what factors influence the price of pizza and the quantity
of pizza sold. She would develop a model that described the behavior of pizza
buyers, the behavior of pizza sellers, and their interaction in the market for pizza.
For example, the economist supposes that the quantity of pizza demanded by
consumers Q d depends on the price of pizza P and on aggregate income Y. This
relationship is expressed in the equation
Q d 5 D(P, Y ),
where D( ) represents the demand function. Similarly, the economist supposes
that the quantity of pizza supplied by pizzerias Q s depends on the price of pizza
FIGURE 1-4
Exogenous Variables
Model
Endogenous Variables
How Models Work Models are simplified theories that show the key
relationships among economic variables. The exogenous variables are
those that come from outside the model. The endogenous variables
are those that the model explains. The model shows how changes in
the exogenous variables affect the endogenous variables.
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The Science of Macroeconomics | 7
P and on the price of materials Pm, such as cheese, tomatoes, flour, and anchovies.
This relationship is expressed as
Q s 5 S(P, Pm ),
where S( ) represents the supply function. Finally, the economist assumes that
the price of pizza adjusts to bring the quantity supplied and quantity demanded
into balance:
Q s 5 Q d.
These three equations compose a model of the market for pizza.
The economist illustrates the model with a supply-and-demand diagram, as in
Figure 1-5.The demand curve shows the relationship between the quantity of pizza
demanded and the price of pizza, holding aggregate income constant.The demand
curve slopes downward because a higher price of pizza encourages consumers to
buy less pizza and switch to, say, hamburgers and tacos.The supply curve shows the
relationship between the quantity of pizza supplied and the price of pizza, holding
the price of materials constant. The supply curve slopes upward because a higher
price of pizza makes selling pizza more profitable, which encourages pizzerias to
produce more of it. The equilibrium for the market is the price and quantity at
which the supply and demand curves intersect. At the equilibrium price, consumers choose to buy the amount of pizza that pizzerias choose to produce.
This model of the pizza market has two exogenous variables and two endogenous variables. The exogenous variables are aggregate income and the price of
FIGURE 1-5
Price of pizza, P
Supply
Market
equilibrium
Equilibrium
price
Demand
Equilibrium
quantity
Quantity of pizza, Q
The Model of Supply and
Demand The most famous
economic model is that of
supply and demand for a
good or service—in this case,
pizza. The demand curve is
a downward-­sloping curve
relating the price of pizza to
the quantity of pizza that
consumers demand. The
supply curve is an upward-­
sloping curve relating the
price of pizza to the quantity of pizza that pizzerias
supply. The price of pizza
adjusts until the quantity
supplied equals the quantity
demanded. The point where
the two curves cross is the
market equilibrium, which
shows the equilibrium price
of pizza and the equilibrium
quantity of pizza.
8 | P A R T
I
Introduction
materials. The model does not attempt to explain them but instead takes them as
given (perhaps to be explained by another model). The endogenous variables are
the price of pizza and the quantity of pizza exchanged. These are the variables
that the model attempts to explain.
The model can be used to show how a change in one of the exogenous
variables affects both endogenous variables. For example, if aggregate income
increases, then the demand for pizza increases, as in panel (a) of Figure 1-6.
The model shows that both the equilibrium price and the equilibrium quantity of pizza rise. Similarly, if the price of materials increases, then the supply of
pizza decreases, as in panel (b) of Figure 1-6. The model shows that in this case
the equilibrium price of pizza rises and the equilibrium quantity of pizza falls.
FIGURE 1 -6
(a) A Shift in Demand
Changes in Equilibrium Price of pizza, P
S
P2
P1
D2
D1
Q1
Q2
Quantity of pizza, Q
(b) A Shift in Supply
Price of pizza, P
S2
S1
P2
P1
D
Q2
Q1
Quantity of pizza, Q
In panel (a), a rise in
aggregate income causes
the demand for pizza to
increase: at any given price,
consumers now want to
buy more pizza. This is
represented by a rightward
shift in the demand curve
from D1 to D2. The market
moves to the new intersection of supply and demand.
The equilibrium price rises
from P1 to P2, and the
equilibrium quantity of
pizza rises from Q1 to Q2.
In panel (b), a rise in the
price of materials decreases
the supply of pizza: at any
given price, pizzerias find
that the sale of pizza is less
profitable and therefore
choose to produce less
pizza. This is represented by
a leftward shift in the supply curve from S1 to S2. The
market moves to the new
intersection of supply and
demand. The equilibrium
price rises from P1 to P2,
and the equilibrium quantity falls from Q1 to Q2.
CHAP T E R
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The Science of Macroeconomics | 9
Thus, the model shows how changes either in aggregate income or in the price
of materials affect price and quantity in the market for pizza.
Like all models, this model of the pizza market makes simplifying assumptions.
The model does not take into account, for example, that every pizzeria is in a
different location. For each customer, one pizzeria is more convenient than the
others, and thus pizzerias have some ability to set their own prices. The model
assumes that there is a single price for pizza, but in fact there could be a different
price at every pizzeria.
How should we react to the model’s lack of realism? Should we discard the
simple model of pizza supply and demand? Should we attempt to build a more
complex model that allows for diverse pizza prices? The answers to these questions depend on our purpose. If our goal is to explain how the price of cheese
affects the average price of pizza and the amount of pizza sold, then the diversity
of pizza prices is probably not important. The simple model of the pizza market
does a good job of addressing that issue. Yet if our goal is to explain why towns
with ten pizzerias have lower pizza prices than towns with only two, the simple
model is less useful.
The art in economics lies in judging when a simplifying assumption (such as
assuming a single price of pizza) clarifies our thinking and when it misleads us.
F Y I
Using Functions to Express Relationships
Among Variables
All economic models express relationships among
economic variables. Often, these relationships
are expressed as functions. A function is a mathematical concept that shows how one variable
depends on a set of other variables. For example,
in the model of the pizza market, we said that the
quantity of pizza demanded depends on the price
of pizza and on aggregate income. To express
this, we use functional notation to write
Q d 5 D(P, Y ).
This equation says that the quantity of pizza
demanded Q d is a function of the price of pizza P
and aggregate income Y. In functional notation,
the variable preceding the parentheses denotes
the function. In this case, D( ) is the function expressing how the variables in parentheses
determine the quantity of pizza demanded.
If we knew more about the pizza market, we could
give a numerical formula for the quantity of pizza
demanded. For example, we might be able to write
Q d 5 60 2 10P 1 2Y.
In this case, the demand function is
D(P, Y ) 5 60 2 10P 1 2Y.
For any price of pizza and aggregate income,
this function gives the corresponding quantity
of pizza demanded. For example, if aggregate
income is $10 and the price of pizza is $2, then
the quantity of pizza demanded is 60 pies; if the
price of pizza rises to $3, the quantity of pizza
demanded falls to 50 pies.
Functional notation allows us to express the
general idea that variables are related, even
when we do not have enough information to
indicate the precise numerical relationship.
For example, we might know that the quantity
of pizza demanded falls when the price rises
from $2 to $3, but we might not know by
how much it falls. In this case, functional
notation is useful: as long as we know that
a relationship among the variables exists, we
can express that relationship using functional
notation.
10 | P A R T
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Introduction
Simplification is a necessary part of building a useful model: any model constructed to be completely realistic would be too complicated for anyone to
understand. Yet if models assume away features of the economy that are crucial
to the issue at hand, they may lead us to conclusions that do not hold in the real
world. Economic modeling therefore requires care and common sense.
The Use of Multiple Models
Macroeconomists study many facets of the economy. For example, they examine
the role of saving in economic growth, the impact of minimum-wage laws on
unemployment, the effect of inflation on interest rates, and the influence of trade
policy on the trade balance and exchange rate.
Economists use models to address all of these issues, but no single model can
answer every question. Just as carpenters use different tools for different tasks,
economists use different models to explain different economic ­phenomena.
Students of macroeconomics therefore must keep in mind that there is no
single “correct” model that is always applicable. Instead, there are many models,
each of which is useful for shedding light on a different facet of the economy.
The field of macroeconomics is like a Swiss army knife—a set of complementary but distinct tools that can be applied in different ways in different
circumstances.
This book presents many different models that address different questions
and make different assumptions. Remember that a model is only as good as its
assumptions and that an assumption that is useful for some purposes may be
misleading for others. When using a model to address a question, the economist
must keep in mind the underlying assumptions and judge whether they are reasonable for studying the matter at hand.
Prices: Flexible Versus Sticky
Throughout this book, one group of assumptions will prove especially
important—­those concerning the speed at which wages and prices adjust to
changing economic conditions. Economists normally presume that the price
of a good or a service moves quickly to bring quantity supplied and quantity
demanded into balance. In other words, they assume that markets are normally in
equilibrium, so the price of any good or service is found where the supply and
demand curves intersect. This assumption, called market clearing, is central to
the model of the pizza market discussed earlier. For answering most questions,
economists use market-clearing models.
Yet the assumption of continuous market clearing is not entirely realistic. For
markets to clear continuously, prices must adjust instantly to changes in supply
and demand. In fact, many wages and prices adjust slowly. Labor contracts often
set wages for up to three years. Many firms leave their product prices the same
for long periods of time—for example, magazine publishers typically change
their newsstand prices only every three or four years. Although market-clearing
CHAP T E R
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The Science of Macroeconomics | 11
models assume that all wages and prices are flexible, in the real world some
wages and prices are sticky.
The apparent stickiness of prices does not make market-clearing models useless. After all, prices are not stuck forever; eventually, they adjust to changes in
supply and demand. Market-clearing models might not describe the economy at
every instant, but they do describe the equilibrium toward which the economy
gravitates. Therefore, most macroeconomists believe that price flexibility is a
good assumption for studying long-run issues, such as the growth in real GDP
that we observe from decade to decade.
For studying short-run issues, such as year-to-year fluctuations in real GDP
and unemployment, the assumption of price flexibility is less plausible. Over
short periods, many prices in the economy are fixed at predetermined levels.
Therefore, most macroeconomists believe that price stickiness is a better assumption for studying the short-run behavior of the economy.
Microeconomic Thinking and Macroeconomic Models
Microeconomics is the study of how households and firms make decisions
and how these decisionmakers interact in the marketplace. A central principle
of microeconomics is that households and firms optimize—they do the best they
can for themselves given their objectives and the constraints they face. In microeconomic models, households choose their purchases to maximize their level of
satisfaction, which economists call utility, and firms make production decisions
to maximize their profits.
Because economy-wide events arise from the interaction of many households
and firms, macroeconomics and microeconomics are inextricably linked. When
we study the economy as a whole, we must consider the decisions of individual
economic actors. For example, to understand what determines total consumer
spending, we must think about a family deciding how much to spend today
and how much to save for the future. To understand what determines total
investment spending, we must think about a firm deciding whether to build a
new factory. Because aggregate variables are the sum of the variables describing
many ­individual decisions, macroeconomic theory rests on a microeconomic
­foundation.
Although microeconomic decisions underlie all economic models, in many
models the optimizing behavior of households and firms is implicit rather than
explicit. The model of the pizza market we discussed earlier is an example.
Households’ decisions about how much pizza to buy underlie the demand for
pizza, and pizzerias’ decisions about how much pizza to produce underlie the
supply of pizza. Presumably, households make their decisions to maximize ­utility,
and pizzerias make their decisions to maximize profit. Yet the model does not
focus on how these microeconomic decisions are made; instead, it leaves these
decisions in the background. Similarly, although microeconomic decisions
underlie macroeconomic phenomena, macroeconomic models do not necessarily focus on the optimizing behavior of households and firms; again, they
sometimes leave that behavior in the background.
12 | P A R T
I
Introduction
F Y I
Nobel Macroeconomists
The Nobel Prize in economics is announced every
October. Over the years, many winners have been
macroeconomists. Here are a few of them, along
with some of their own words about how they
chose their career paths:
Milton Friedman (Nobel 1976): “I graduated
from college in 1932, when the United States was
at the bottom of the deepest depression in its
history before or since. The dominant problem
of the time was economics. How to get out of
the depression? How to reduce unemployment?
What explained the paradox of great need on the
one hand and unused resources on the other?
Under the circumstances, becoming an economist seemed more relevant to the burning issues
of the day than becoming an applied mathematician or an actuary.”
James Tobin (Nobel 1981): “I was attracted to
the field for two reasons. One was that economic
theory is a fascinating intellectual challenge,
on the order of mathematics or chess. I liked
analytics and logical argument. . . . The other
reason was the obvious relevance of economics
to understanding and perhaps overcoming the
Great Depression.”
Franco Modigliani (Nobel 1985): “For a while
it was thought that I should study medicine
because my father was a physician. . . . I went to
the registration window to sign up for medicine,
but then I closed my eyes and thought of blood!
I got pale just thinking about blood and decided
under those conditions I had better keep away
from medicine. . . . Casting about for something
to do, I happened to get into some economics
activities. I knew some German and was asked to
translate from German into Italian some articles
for one of the trade associations. Thus I began to
be exposed to the economic problems that were
in the German literature.”
Robert Solow (Nobel 1987): “I came back [to
college after being in the army] and, almost
without thinking about it, signed up to finish my
undergraduate degree as an economics major.
The time was such that I had to make a decision in
a hurry. No doubt I acted as if I were maximizing
an infinite discounted sum of one-period utilities,
but you couldn’t prove it by me. To me it felt as if
I were saying to myself: ‘What the hell.’”
Robert Lucas (Nobel 1995): “In public school
science was an unending and not very well
organized list of things other people had discovered long ago. In college, I learned something
about the process of scientific discovery, but
what I learned did not attract me as a career
­possibility. . . . What I liked thinking about were
politics and social issues.”
George Akerlof (Nobel 2001): “When I went to
Yale, I was convinced that I wanted to be either an
economist or an historian. Really, for me it was a
distinction without a difference. If I was going to
be an historian, then I would be an economic historian. And if I was to be an economist, I would
consider history as the basis for my economics.”
Edward Prescott (Nobel 2004): “Through discussion with [my father], I learned a lot about the
way businesses operated. This was one reason
why I liked my microeconomics course so much
in my first year at Swarthmore College. The price
theory that I learned in that course rationalized
what I had learned from him about the way businesses operate. The other reason was the textbook
used in that course, Paul A. Samuelson’s Principles
of Economics. I loved the way Samuelson laid out
the theory in his textbook, so simply and clearly.”
Edmund Phelps (Nobel 2006): “Like most Americans entering college, I started at Amherst College without a predetermined course of study or
without even a career goal. My tacit assumption
was that I would drift into the world of b
­ usiness—
of money, doing something terribly smart. In
the first year, though, I was awestruck by Plato,
Hume, and James. I would probably have gone
into philosophy were it not that my father cajoled
and pleaded with me to try a course in economics, which I did the second year. . . . I was hugely
impressed to see that it was possible to subject
the events in those newspapers I had read about
to a formal sort of analysis.”
Christopher Sims (Nobel 2011): “[My Uncle]
Mark prodded me regularly, from about age 13
CHAP T E R
onward, to study economics. He gave me von
Neumann and Morgenstern’s Theory of Games
for Christmas when I was in high school. When
I took my first course in economics, I remember
arguing with him over whether it was possible for
the inflation rate to explode upward if the money
supply were held constant. I took the monetarist
position. He questioned whether I had a sound
argument to support it. For years I thought he
1
The Science of Macroeconomics | 13
was having the opposite of his intended effect,
and I studied no economics until my junior
year of college. But as I began to doubt that I
wanted to be immersed for my whole career in
the abstractions of pure mathematics, Mark’s
efforts had left me with a pretty clear idea of an
alternative.”
If you want to learn more about the Nobel Prize
and its winners, go to http://www.nobelprize.org.1
1-3 How This Book Proceeds
This book has six parts. This chapter and the next make up Part One, the
“­Introduction.” Chapter 2 discusses how economists measure economic variables, such as aggregate income, the inflation rate, and the unemployment rate.
Part Two, “Classical Theory: The Economy in the Long Run,” presents the
classical model of how the economy works. The key assumption of the classical
model is that prices are flexible. That is, with rare exceptions, the classical model
assumes that markets clear. The assumption of price flexibility greatly simplifies
the analysis, which is why we start with it.Yet because this assumption accurately
describes the economy only in the long run, classical theory is best suited for
analyzing a time horizon of at least several years.
Part Three, “Growth Theory: The Economy in the Very Long Run,” builds on
the classical model. It maintains the assumptions of price flexibility and market
clearing but adds a new emphasis on growth in the capital stock, the labor force,
and technological knowledge. Growth theory is designed to explain how the
economy evolves over a period of several decades.
Part Four, “Business Cycle Theory: The Economy in the Short Run,” examines the behavior of the economy when prices are sticky. The non-marketclearing model developed here is designed to analyze short-run issues, such as
the reasons for economic fluctuations and the influence of government policy
on those fluctuations. It is best suited for analyzing the changes in the economy
we observe from month to month or from year to year.
The last two parts of the book cover various topics to supplement, reinforce,
and refine our long-run and short-run analyses. Part Five, “Topics in Macroeconomic Theory,” presents advanced material of a somewhat theoretical nature,
including macroeconomic dynamics, models of consumer behavior, and theories
of firms’ investment decisions. Part Six, “Topics in Macroeconomic Policy,” considers what role the government should have in the economy. It discusses the
policy debates over stabilization policy, government debt, and financial crises.
1
The first five quotations are from William Breit and Barry T. Hirsch, eds., Lives of the Laureates, 4th ed.
(Cambridge, MA: MIT Press, 2004). The sixth, seventh, and ninth are from the Nobel Web site. The
eighth is from Arnold Heertje, ed., The Makers of Modern Economics, vol. II (Aldershot, U.K.: Edward
Elgar Publishing, 1995).
14 | P A R T
I
Introduction
Summary
1.Macroeconomics is the study of the economy as a whole, including growth
in incomes, changes in prices, and the rate of unemployment. Macroeconomists attempt both to explain economic events and to devise policies to
improve economic performance.
2.To understand the economy, economists use models—theories that simplify
reality in order to reveal how exogenous variables influence endogenous
variables. The art in the science of economics lies in judging whether a
model captures the important economic relationships for the matter at
hand. Because no single model can answer all questions, macroeconomists
use different models to look at different issues.
3.A key feature of a macroeconomic model is whether it assumes that prices
are flexible or sticky. According to most macroeconomists, models with
flexible prices describe the economy in the long run, whereas models with
sticky prices offer a better description of the economy in the short run.
4.Microeconomics is the study of how firms and individuals make decisions
and how these decisionmakers interact. Because macroeconomic events
arise from many microeconomic interactions, all macroeconomic models
must be consistent with microeconomic foundations, even if those foundations are only implicit.
K E Y
C O N C E P T S
Macroeconomics
Real GDP
Inflation and deflation
Unemployment
Q U E S T I O N S
Recession
Depression
Models
Endogenous variables
F O R
R E V I E W
1.Explain the difference between macroeconomics
and microeconomics. How are these two fields
related?
2.Why do economists build models?
Exogenous variables
Market clearing
Flexible and sticky prices
Microeconomics
3.What is a market-clearing model? When is it
appropriate to assume that markets clear?
CHAP T E R
P R O B L E M S
A N D
1
The Science of Macroeconomics | 15
A P P L I C AT I O N S
1.List three macroeconomic issues that have been
in the news lately.
2.What do you think are the defining characteristics of a science? Do you think macroeconomics
should be called a science? Why or why not?
3.Use the model of supply and demand to explain
how a fall in the price of frozen yogurt would
affect the price of ice cream and the quantity of
ice cream sold. In your explanation, identify the
exogenous and endogenous variables.
4.How often does the price you pay for a haircut
change? What does your answer imply about the
usefulness of market-clearing models for analyzing the market for haircuts?
To access online learning resources, visit
for Macroeconomics, 9e
at www.macmillanhighered.com/launchpad/mankiw9e